Hi all!
Stan Sandler wrote:"I find it curious that with their colony cycle nearing its
end the yellow jackets are working furiously.  They are robbing from any
weak colonies or...."
 
I heard this explanation of Yellow jackets quest for sweets: They feed their
larvaes with meat (carcasses, larvaes of other insects etc.). In return the
Yellow jacket larvae is producing a sweet substance (honeydew?). This
sweet substance is the only thing that makes the yellow jackets care for
their larvae. When brood rearing slows down/ends in autumn they seek for
sweet experiences elsewhere.
Regards Morten